Systems for the control of the supply of air under pressure and water to dental handpieces are already known, particularly to several drills operated by turbines, for which it is possible to supply air under pressure to the handpiece by depressing a suitable pedal, or simultaneously water and air under pressure required to activate the turbine and to provide a water spray, by depressing another suitable pedal.
Since by depressing the above-mentioned pedals, air under pressure, or water and air under pressure, are available simultaneously to all handpieces of the type mounted on a suitable support near the chair for the patient, steps are taken to permit the effective flow only to the handpiece which, at any given time, is removed from the support for use. In this manner, one avoids the flow of air under pressure and eventually water and air under pressure to the handpieces that are not being used and which remain in their respective supports and no air activates the handpieces not in use.
The above special steps involve the use of valves incorporated or otherwise mounted on the bracket which holds the support onto which the handpieces are hung. The valves remain closed when the handpieces are left in said supports.
The mechanical systems are made in the form of supports shaped like a lever or balance-spring which move under the weight of the handpieces against the action of a spring-loaded mechanism for closing the valve for the air under pressure and for water.
Also known are techniques which include ball bearings which are pressed against a seat to impede the flow of air under pressure and water to the respective tubings which lead to the handpiece. The removal of a handpiece from the relative support permits the movement of the ball bearings and the restoration of the flow of air and water under pressure to the handpiece itself.
Other more modern systems embody the use of fluidic valves having sensors which emerge in the supports and are obstructed by the handpieces when the latter are placed in said supports.
The above-mentioned known systems present numerous problems. The problem common to all is the presence of a valve operated by a pedal for the control of the flow of water to the handpieces. In case of failure, due for example to a damaged seal, there is the risk of flooding the office in which the equipment is installed, and it is not possible to correct the problem without obtaining the assistance of technical personnel.
In addition, the valve systems, the opening and closings of which depend on whether or not the handpiece is hung on the support, present additional inconveniences which add to the problem mentioned above. Therefore, for example, mechanical systems are not too dependable and are easily subject to failures which require the attention of specialized personnel to be repaired.
The fluidic valves, two of which are required for each handpiece, are very expensive and if there is a failure, even though they do not occur too frequently, they require the attention of experts to be repaired or replaced.